Rocket Launch Project
Kian Blewett
Partners- Nick Abbott and Steven Kaufman
I. Materials
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Materials
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Approximate
Cost
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Two 2-liter bottles
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$7.00
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One roll of duct tape
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$4.50
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Stickers
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$3.00
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2 pairs of socks
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$10.00
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Egg (provided)
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$0.25
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Cardboard
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free
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Dental floss
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$1.50
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Trash bag
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$1.00
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7 pennies
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$0.07
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Total
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$27.32
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II. Procedure
Steps:
1. Take one of the two bottles, and using scissors or an x-acto knife, carefully cut the bottle roughly in half. If anything, you want the side with the neck and bottle cap to be slightly longer after you make the incision. You no longer need the bottom half of that bottle, while the top half will serve as your egg capsule (which will deploy from the fuel cell, which is the other bottle).
2. Press a small square of duct tape in to the spout of the cut bottle from the inside. Then, screw off the bottle cap, and insert your 7 pennies in to the neck. The duct tape should keep the pennies securely in the spout once you screw the cap back on. This will serve to provide some weight to the nose of your rocket, and by taking the cap of you can easily adjust the number of pennies you have in the nose.
3. Press one of the four socks in to the neck of the bottle, and then duct tape it down. Then, take two socks and create a ring of sorts by duct taping one end of one sock to the end of another. The place this ring above the first sock. This should effectively create a little hole that, when the time comes, your egg will fit nicely in to. The last sock will be place on top of the egg after you put the egg in his hole.
4. The last step to complete for the egg capsule will be the parachute. First, take the trash bag and cut it so that you shave of 1/3 of the bag, leaving you with a smaller, more manageable bag. Then, make six small holes around the edge of the bag, about 4 centimeters in from the lip. Make sure the holes are evenly spaced around the bag.
5. Now, cut 6 corresponding hole on the edge of the egg capsule. When you have made all of your holes, you will use dental floss to connect each hole on the egg capsule to its corresponding hole in the parachute. Cut approximately 50 cm of dental floss, and thread it through both holes. Then make a double knot to ensure it won't come apart. Do this with all six holes. Also, keep in mind not to tie the parachute hole to the wrong egg capsule hole. If you do this, the dental floss will become entangled when the parachute deploys.
Now your egg capsule is done. The next steps will involve the fuel cell, which is the un-cut bottle.
6. The first step will be to cut out the fins from cardboard. Use a sharpie to draw out the shape of a parallelogram. After some research, I found that this was the most effective shape. Make the parallelogram 7 cm in width and about 15 cm in length. Use scissors or an x-acto knife to cut the fin out of the cardboard. Now that you have your first fin, you can use it to trace out the other two fins.
7. When you have 3 equal fins, you now have to fasten them to the fuel cell. Use a tape measure to find the circumference of the bottle, and then divide that by 3, making 3 marks with a sharpie so you know where to put your fins so that they are evenly spaced out.
8. Fasten the fins to the rocket, closest to the side of the neck (because while your rocket is flying, this will actually be at the back of the rocket). Use duct tape. Be especially careful with this step, because you want the fins to be as aerodynamic as possible. So, make sure there are no wrinkles in the tape, and smooth off any areas with holes with more tape. Also, be mindful of where you are putting your fins. I put the fins on the wrong end of the fuel cell at first, and then had to restart. Remember, they go on the end nearest to the bottle cap. When you're done, you're fuel cell should look like this:
9. Decorate with stickers!
10. When you are ready for launch, the egg capsule should fit nicely on to the end of the fuel cell (what was once the base of the bottle). Before you finalize it, make sure you have nothing loose, unorganized, broken, etc.
Now your rocket should look like this:
III. Results
In the end, our rocket preformed very well. The weather was near perfect conditions and we were ready to see our beloved Mr. Eggsy take a trip to the heavens. We actually had the highest rocket and the rocket that was longest in the air. This was great to see, as it sailed high, very steadily. We did have one huge malfunction, however, which is that the egg capsule failed to detach, and thus the parachute failed to deploy (except on impact). The cushioning on the inside was not enough to protect the egg without deployment, so Mr. Eggsy was essentially "scrambled". The launch itself went very smoothly, and for the first half of the launch everything went very well (in fact, exceeded standards!).
IV. Conclusion
Ultimately I was very happy with our rocket's performance, even considering the failure to deploy the egg capsule. I think there are several factors that set our rocket apart. Firstly, I think the choice to add quite a bit of weight to the nose was a great decision, because it gave our rocket a very smooth flight, due to the momentum being in the front. Furthermore, I think the fuel cell was constructed very well. The fins were a great aerodynamic shape, spaced out evenly (which allowed a smoother flight), and fastened on well. However, there are also a few things I would want to change about the rocket, mostly regarding the egg capsule. Because the capsule was kept on by pushing the fuel cell in to the capsule, I don't think it was loose enough to detach. Especially considering the fuel cell would push further into the capsule on launch due to inertia. So to fix this, we would have to come up with a way to have the egg capsule stable upon launch, but loose enough to detach on the way down. A solution could be having the egg capsule fit in to the fuel cell with a third piece, rather than vice versa. This way the momentum of the fuel cell would keep the rocket intact on the way up, but ideally it would detach after it reaches its peak. That being said, it might cause a lot of drag that would not be the case if we kept it the way we had it.
VI. Calculations
1) I believe our value was more accurate because it is based entirely off of the time given, which is the most reliable fact. The time given to us is 3.62, but because in order to find the highest point, you can only look at the first half of the projectile motion. So I halved the given time so that Vf would equal 0 (because at the apex it is motionless). This gave me a lower value than I expected, but I checked it several times with alternate equations to make sure (not pictured). I also plugged in the full time (3.62), because if my thought process is correct, this should yield 0 m, because displacement is back to where it started.
2) It is simple to find the Vi because you have Vf, Ag, and time. Again, you use 1.81 seconds instead of 3.62, because this way you can use vf=0.
3) Force Body Diagrams
